Has the approach to verbs in v2 changed?

[ericnewton76]

Issue by ravensorb
Thursday Nov 02, 2017 at 18:53 GMT
Originally opened as gsscoder/commandline#500

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I was reviewing the code and the following wiki for vers
https://github.com/gsscoder/commandline/wiki/Latest-Version and I cannot see how they line up.

Ex - the following will not compile

var result = CommandLine.Parser.Default.ParseArguments<AddOptions, UpdateOptions, DeleteOptions(args).MapResult(
    (AddOptions aopts) => {},
    (UpdateOptions upopts) => {},
    (DeleteOptions dopts) => {});

It complains that there is no support for more than one Generic and from looking at the code, I didn't see any overrides or extensions to ParseArguments that supports multiple generics. So I was curious if the approach had changed.

[ericnewton76]

Comment by nemec
Thursday Nov 02, 2017 at 19:08 GMT

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Two things:

1. MapResult has a final delegate parameter that is required to be of type IEnumerable<Error> for any errors.
2. Each delegate must return a value - they are Func not Action and each value must be the same type. If you quickly add return ""; to each of those it compiles for me.

[ericnewton76]

Comment by ravensorb
Thursday Nov 02, 2017 at 19:16 GMT

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Cool So i just tried build 2.1.1-beta and I cannot get the snippet above to compile

error CS0305: Using the generic method 'Parser.ParseArguments<T>(IEnumerable<string>)' requires 1 type arguments

[ericnewton76]

Comment by nemec
Thursday Nov 02, 2017 at 19:20 GMT

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Did it mention a file/line number?

[ericnewton76]

Comment by ravensorb
Thursday Nov 02, 2017 at 19:23 GMT

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Its in my simple test app and when I look at the object explorer I only see a ParseArguments and not other overloads for more generic args.

[ericnewton76]

Comment by nemec
Thursday Nov 02, 2017 at 19:53 GMT

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Sorry I misread and thought you were building the source code of the library. This worked for me on the latest beta:

var result = CommandLine.Parser.Default.ParseArguments<AddOptions, UpdateOptions, DeleteOptions(args).MapResult(
    (AddOptions aopts) => {return ""; },
    (UpdateOptions upopts) => {return ""; },
    (DeleteOptions dopts) => {return ""; },
    (IEnumerable<Error> errs) => {return ""; });

[ericnewton76]

Comment by ravensorb
Thursday Nov 02, 2017 at 20:10 GMT

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That helped -- I found the issue :) It appears you must add the using statement

using CommnadLine;

Without that it doesn't find the extension methods or the Error option.

[mhmd-azeez]

@ericnewton76 Wouldn't it be better to mention the need to add using CommnadLine; in the README.md example as well? Or at least write Parser.Default.ParseArguments instead of CommandLine.Parser.Default.ParseArguments to force the programmer to add a using statement.

Because it's not obvious from the example that these are extension methods and can produce frustrating compilation errors.

[heinermann]

Just ran into this myself, thanks whoever ran into this issue first and shared the fix. 🙏🏻